Powering board from 12V

Machine: Custom built
Board: LaserBoard
Firmware: Smoothie

Question: Since I’m using external drivers for each axis is there any reason I can’t power the board from a 12V supply? The reason I ask is that I want to use the Air Assit FET to switch a 12V solenoid. Obviously I can use an intermediary system to reduce the voltage, but if I don’t have to then it’s one less thing to worry about.

That could be ok, the board will run fine on 12v. The main things we care about are:

  • That the power supply is very clean so that the board does not brown out or act unstable.
  • That the respectable limits are observed for the Air Assist FET.
    You would not have a limit due to PSU amperage, but still recommend staying within respectable boundaries. LaserBoard Air Assist Control

Thanks Ray. I’ll take a look at what 12V supplies I’ve got laying around and make sure I pick a good one. The solenoid is marked as only needing 29mA, but I’m not convinced of that so I’ll hook it up away from the board and do some testing with it as well.

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29mA seems extremely low, but then again I’m imagining a large metal air solenoid. The small stuff should still take a few amps, which is fine, but still an order of magnitude or two off of your spec :slight_smile:

Got a picture of your solenoid?

I’ll get a picture later. I should say that it has 29mA marked on it, rather than it’s marked as only needing 29mA. There’s no indication as to what that actually refers to. It is also marked as 12V 4.0W, which if that refers to its requirements immediately suggests 333mA, which is why I’m not convinced. Of course I could just go look it up online …

Here it is: https://ussolid.com/ussolid-1-8-3-way-2-position-pneumatic-electric-solenoid-valve-dc-12-v.html

Still no indication as to what the 29mA refers to, but there’s a picture of the label I was going from. I’ll hook it up to an off board supply and measure the current draw before I attach it directly to the LaserBoard.

Ohms law checks out. Interesting. Should be fine anyways.

So I haven’t hooked up the 12V yet, instead I thought I’d just use a couple of resistors as a voltage divider to start with. I checked that I was getting 12V with a M106 and 0V with M107. I confirmed that the solenoid would switch at 12V with a draw of 0.33A on my bench top power supply. But when I plug the solenoid in to the leads I have coming from the LaserBoard it’s not working. Measuring the voltage at the connector between the two sets of leads I get less than 1V. I then tried with a regular automotive relay and same thing, (except I now get just under 2V at the relay). I’m connecting to the screw terminal, and like I said I’m getting 12V after the voltage divider. I used 1Kohm resistors, because I don’t know any better, could that be the problem?

A resistive voltage divider will be extremely limited on the current it can provide. If you’re using 1/4W resistors you’re limited to roughly 0.02A through the divider before the resistors start to heat up and contribute significantly to voltage drop.

If you have an adjustable bench supply just feed it 12V from there and take the divider out of the equation.

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Or to paraphrase Einstein, if it’s not working, the sane thing to do next would be to try a different way. :slight_smile:

Thanks for the confirmation. I’ll just go back to the original plan and hook up a 12V power supply. I only tried the voltage divider as a temporary measure anyway.

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